Soils at the ground surface and within several feet of the surface (“surface soils”) are typically less consolidated than soils further from the surface (“deep soils”). Surface soils are generally more variable and possess lower strength than deep soils. In current civil engineering and building construction practice, the bottom of a building floor slab, building footings, or both, may be placed in surface soils. When the use of piles or piers is not economical the engineer/builder either excavates to the bottom of the objectionable surface soils and replaces them with better materials, or attempts to improve the objectionable surface soil in-situ by surface rolling with various kinds of conventional compaction equipment. With either of these approaches, subsequent testing is typically needed to confirm that the desired degree of soil improvement has been achieved, which results in additional project cost and time. The present inventor has recognized a need for a better method for improving surface soils to depths several feet below the ground surface. The present inventor has also recognized a need for less costly, faster, and quantifiable in-situ surface soil improvement apparatuses and methods to reduce construction time, increase construction efficiency, and allow results to be observed directly as the soil improvement progresses.
The present inventor has recognized that there are disadvantages with excavating and replacing objectionable surface soil and with current compaction equipment and techniques. Excavating and replacing loose surface soils beneath planned floor slabs or footings requires an adequate working area on the site for safely back sloping the excavation side walls, and for temporarily stockpiling the excavated surface soils while the excavation and replacement proceeds. Additionally, the proximity of nearby existing structures can necessitate expensive shoring and bracing of excavation sidewalls. A further disadvantage of the excavation-replacement option is that changing soil moisture content during the work (typically caused by either drying in hot weather or wetting in rainy weather) can reduce the feasibility of achieving the desired degree of compaction of the replacement material. Disadvantages of current compaction equipment and techniques used on existing surface soils is that changing soil moisture content during the work can reduce the feasibility of achieving the desired degree of compaction, and independent testing is commonly needed to determine whether the desired degree of compaction has been achieved. The methods and apparatus disclosed herein may help eliminate these problems by improving the surface soils in-place without removing and replacing the surface soils.
Additional aspects and advantages will be apparent from the following detailed description of preferred embodiments, which proceeds with reference to the accompanying drawings.